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Forum Index : Electronics : Battery charging question
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mad jack Newbie  Joined: 26/06/2020 Location: United StatesPosts: 11 |
This is for a small solar generator trailer I have two small banks of batteries Bank 1 is four 210Ah 6 volt batteries connected S2-P2 for 12 volts at 420 Ah to run a small psw inverter (3000 china watts). the second set of batteries are spiral cell deep cycle (optima yellow top) 55Ah each connected P2 for 12 volts at 110 Ah and will power 12 volt work lights (led)and cooling /ventilation fans inside the trailer . Charge Controller is connected to main bank . My question is can I use a mosfet to connect the second set of batteries to the first set when charging voltage is above a pre set level (13.75v) to charge set 2 . I know I can use voltage divider to do this but unsure what will happen when the mosfet turns on . Option #2 if I split charge controller output with two diodes will both banks charge without causing trouble for controller voltage sample All ideas are welcome and thanks for taking your time to read this |
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wiseguy Guru  Joined: 21/06/2018 Location: AustraliaPosts: 1156 |
My first thoughts on this is that if the 55AH battery is relatively flat then it may be problematic to turn on a switch (the Mosfet) when the main battery bank is at 13.75V. Connecting the two battery banks instantaneously in parallel can have issues as quite large currents can flow for a while until the battery voltages are essentially balanced. I have always viewed larger batteries as resembling the rock of Gibraltar in that the voltage is never going to budge instantaneously so any voltage potential difference can lead to the large currents limited by cell internal resistance and any wiring/switch impedance. With regard to splitting the charge controller to the two batteries, unless the controller has a separate sense wire that can be attached directly to the main battery bank, the controller may not charge the batteries correctly due to the diode voltage drop. Using 2 decent "gutsy" schottky diodes would help reduce this issue if there is no Vsense connection. Another possible method involves a current controlled buck switchmode regulator that is enabled at 13.75V and limits the charge current to a more modest 5 to 20 Amps might work. If it was capable of 100% duty cycle, both batteries would effectively become tied together when the voltages become equal. The schottky diode solution (heatsink probably required) might be best/simplest one as either battery bank becoming very discharged will not flatten the other bank and is essentially an unattended solution. I will be interested to see what other solutions/comments are suggested. Edited 2022-06-24 12:54 by wiseguy If at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
Perhaps I'm missing some information here; simplest solution to to parallel both 12v banks to the single charge controller, each bank is fused at their common 12V junction point. I cannot see why you require splitting the thing into a battery for inverter and other for lights etc; sorry doesn't make any logical sense. Any attempt at using diodes or mosfets will only stuff up the charge controllers battery voltage sense and thus charging end points, - unless it has external remote sensing. |
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| nickskethisniks Guru Joined: 17/10/2017 Location: BelgiumPosts: 458 |
Best sugestions are already given I think. If you want it like it is, you can use a battery charger powered from your inverter. But the buck converter is a more efficient idea. A second solar regulator to your array is another option, you can disconnect the solar panels with a mosfet. If you want to use a single solar controller, a more complex solution could be thinkered. For example, disconnect your solar panels first with a mosfet, Then disconnect battery 1 and Then connect battery 2 and finaly connect solar panels again. You Will need to have some basic programming skills and basic electronics knowledge to design a schematic/pcb. If you don't disconnect your solar panels you might blow it up. Also, your internal controller capacitors will not like being charged up by a big battery, so be carefull. Edited 2022-06-25 21:32 by nickskethisniks |
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| kalvinbrian913 Newbie Joined: 06/08/2022 Location: United StatesPosts: 2 |
I was looking for the business coupon 2022 ideas relate to solar system and I found mostly every thing I want to sell the complete solar system and I need any whole seller anyone can help me to find whole seller for system system setup. |
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